Methods for improving low-temperature properties of biodiesel fuel

ABSTRACT

The present invention is generally directed to novel biodiesel fuel compositions having enhanced low-temperature properties. The present invention is additionally directed to methods (i.e., processes) for making such enhanced biodiesel fuels by improving the low-temperature properties of ester-based biodiesel fuels via in situ enhancement and/or additive enhancement.

FIELD OF THE INVENTION

This invention relates generally to fuel compositions, and particularlyto enhanced biodiesel fuel compositions comprising functionalizedspecies derived from biodiesel, wherein such functionalized species canserve to improve the low-temperature properties of the biodiesel fuelcompositions of which they are a component.

BACKGROUND

Biofuels are of increasing interest for a number of reasons including:(1) they are a renewable resource, (2) their production is lessdependent on geopolitical considerations, (3) they provide thepossibility of a direct replacement of petroleum-based fuels in existingvehicles, and (4) the net greenhouse gas emissions can be substantiallyreduced by virtue of CO₂ uptake by biofuel precursors—particularly inthe case of cellulosic feedstocks. See Pearce, “Fuels Gold,” NewScientist, 23 September, pp. 36-41, 2006.

An easily-obtainable biofuel is vegetable oil, which largely comprisestriglycerides and some free fatty acids. The properties of vegetableoil, however, make it generally inappropriate for use as a directreplacement for petroleum diesel in vehicle engines, as the vegetableoils' viscosities are generally too high and do not burn cleanly enough,thereby leaving damaging carbon deposits on the engine. Additionally,vegetable oils tend to gel at lower temperatures, thereby hinderingtheir use in colder climates. These problems are mitigated when thevegetable oils are blended with petroleum fuels, but still remain animpediment for long-term use in diesel engines. See Pearce, 2006; Huberet al., “Synthesis of Transportation Fuels from Biomass: Chemistry,Catalysts, and Engineering,” Chem. Rev., vol. 106, pp. 4044-4098, 2006.

Transesterification is currently a method used to convert vegetable oilsinto diesel-compatible fuels (i.e., biodiesel) that can be burned inconventional diesel engines. When methanol is used to transesterifyvegetable oil, the resulting biodiesel is primarily composed of methylesters that have long straight chain aliphatic groups attached to acarbonyl group (i.e., fatty acid methyl esters, or FAME). Such biodieselinvariably comprises ester species having regions of unsaturation, i.e.,double bonds, although the amount of such unsaturated ester species canvary widely depending upon its biomass source. See, e.g., Meher et al.,“Technical aspects of biodiesel production by transesterification—areview,” Renewable & Sustainable Energy Reviews, vol. 10, pp. 248-268,2006. While such processing of vegetable oil enhances their ability tobe used as fuels, the resulting ester-based compositions still havelow-temperature properties that are generally inferior to those ofconventional petroleum-based diesel.

Accordingly, compositions and/or methods for improving thelow-temperature properties of biodiesel made by transesterification ofvegetable oils would be quite useful, particularly wherein they impartthe resulting fuel with greater seasonal and geographic utility.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is generally directed to novel biodiesel fuelcompositions having enhanced low-temperature properties. The presentinvention is additionally directed to methods (i.e., processes) formaking such enhanced biodiesel fuels by improving the low-temperatureproperties of ester-based biodiesel fuels (vide supra) via in situenhancement/modification and/or additive enhancement.

In some embodiments, the present invention is directed to one or moreenhanced biodiesel fuel compositions, said compositions comprising: (a)an ester-based biodiesel component; and (b) a functionalized estercomponent comprising functionalized ester species having the generalformula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; wherein R₂ and R₃ are independently selected from the groupconsisting of C1 to C10 alkyl moieties, C1 to C10 alkenyl moieties, andcombinations thereof, wherein R₄ is selected from the group consistingof C2 to C20 alkyl moieties and C2 to C20 alkenyl moieties; wherein R₅is selected from the group consisting of —H, hydroxyl (—OH), and C2 toC20 ester-forming carboxylate (RCOO—) functional species/moieties; andwherein the functionalized ester species amount to at least about 0.1weight percent of the enhanced biodiesel fuel.

In some embodiments, the present invention is directed to one or moremethods of a first type for improving low-temperature properties ofbiodiesel fuel, such methods comprising the steps of: (a) providing abiodiesel fuel comprising unsaturated ester molecules; (b) treating thebiodiesel fuel so as to react at least some of the unsaturated estermolecules contained therein with an oxidizing species to convert atleast some of the unsaturated ester molecules to epoxy-ester species andprovide for an epoxy-ester-containing biodiesel fuel; and (c) reactingat least some of the epoxy-ester species in the epoxy-ester-containingbiodiesel fuel with one or more reactants to produce an enhancedbiodiesel fuel composition comprising functionalized ester species (videsupra), wherein such enhancement of the biodiesel fuel at leastpartially results from an improvement in the low-temperature propertiesof said enhanced biodiesel fuel relative to those of the biodiesel fuelfrom which it was derived.

In some embodiments, the present invention is directed to one or moremethods of a second type for improving low-temperature properties ofbiodiesel fuel, such methods comprising the steps of: (a) providing afirst biodiesel fuel comprising unsaturated ester molecules; (b)extracting at least some of the unsaturated ester molecules from thefirst biodiesel fuel so as to provide an extract; (c) treating theextract with an oxidizing species so as to convert at least some of theunsaturated ester molecules contained therein into epoxy-ester speciesand provide for an epoxy-ester-containing intermediate; (d) reacting atleast some of the epoxy-ester species in the epoxy-ester-containingintermediate with one or more reactants to produce a functionalizedester composition comprising functionalized ester species; and (e)adding the functionalized ester composition to a second biodiesel fuelso as to provide for an enhanced biodiesel fuel.

The foregoing has outlined rather broadly the features of the presentinvention in order that the detailed description of the invention thatfollows may be better understood. Additional features and advantages ofthe invention will be described hereinafter which form the subject ofthe claims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates, in stepwise fashion, a first type of method forgenerating an enhanced diesel fuel composition, in accordance with someembodiments of the present invention;

FIG. 2 illustrates, in stepwise fashion, a second type of method forgenerating an enhanced diesel fuel composition, in accordance with someembodiments of the present invention; and

FIG. 3 depicts the formation of an epoxy-ester species, in accordancewith some embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION 1. Introduction

As mentioned above, embodiments of the present invention are generallydirected to novel biodiesel fuel compositions having enhancedlow-temperature properties, and to methods (i.e., processes) for makingsuch compositions. Such novel biodiesel fuel compositions are generallylipid- or ester-based, but can also be the product(s) of blending withconventional diesel and/or other bio-derived fuels. Method of makingsuch fuels involve the incorporation of low-temperatureproperty-improving species in the fuel composition, wherein such speciescan be incorporated in the composition in situ and/or as an additive.

2. Definitions

Certain terms and phrases are defined throughout this description asthey are first used, while certain other terms used in this descriptionare defined below:

The prefix “bio,” as used herein, refers to an association with arenewable resource of biological origin, such resources generally beingexclusive of fossil fuels.

A “biologically-derived oil,” as defined herein, refers to anytriglyceride-containing oil that is at least partially derived from abiological source such as, but not limited to, crops, vegetables,microalgae, and the like. Such oils may further comprise free fattyacids. The biological source is henceforth referred to as “biomass.” Formore on the advantages of using microalgae as a source of triglycerides,see R. Baum, “Microalgae are Possible Source of Biodiesel Fuel,” Chem. &Eng. News, vol. 72(14), pp. 28-29, 1994.

“Triglyceride,” as defined herein, refers to class of molecules havingthe following molecular structure:

where x, y, and z can be the same or different, and wherein one or moreof the branches defined by x, y, and z can have unsaturated regions.

A “carboxylic acid” or “fatty acid,” as defined herein, is a class oforganic acids having the general formula:

where “R” is generally a saturated (alkyl) hydrocarbon chain or a mono-or polyunsaturated (alkenyl) hydrocarbon chain.

“Lipids,” as defined herein, broadly refers to the class of moleculescomprising fatty acids, and tri-, di-, and monoglycerides.

“Hydrolysis” of triglycerides yields free fatty acids and glycerol, suchfatty acid species also commonly referred to as carboxylic acids (seeabove).

“Transesterification,” or simply “esterification,” refers to thereaction between a fatty acid or ester (e.g., a triglyceride) and analcohol to yield an ester species.

“Transportation fuels,” as defined herein, refer to hydrocarbon-basedfuels suitable for consumption by vehicles. Such fuels include, but arenot limited to, diesel, gasoline, jet fuel and the like.

“Diesel fuel,” as defined herein, is a material suitable for use indiesel engines and conforming to the current version of at least one ofthe following specifications: ASTM D 975—“Standard Specification forDiesel Fuel Oils”; European Grade CEN 90; Japanese Fuel Standards JIS K2204; The United States National Conference on Weights and Measures(NCWM) 1997 guidelines for premium diesel fuel; and The United StatesEngine Manufacturers Association recommended guideline for premiumdiesel fuel (FQP-1A).

The term “biodiesel,” as used herein, refers to diesel fuel that is atleast significantly derived from a biological source, and which isgenerally consistent with ASTM International Standard Test MethodD-6751. Often, biodiesel is blended with conventional petroleum diesel.B20 is a blend of 20 percent biodiesel with 80 percent conventionaldiesel. B100 denotes pure biodiesel.

An “enhanced biodiesel fuel,” as defined herein, is a biodiesel fuelthat has been modified so as to improve one or more properties relativeto the unmodified fuel. Such modifications can be by way of in situalterations of the fuel composition and/or by supplying additives tosaid composition.

“Cetane rating” or “cetane number,” as defined herein, is a measure ofcombustion efficiency of a diesel fuel. Generally, the higher the cetanenumber, the more easily the fuel self-ignites under compression (ashappens in a diesel engine). Additives are often added to increase adiesel fuel's cetane number. Note that pure cetane (hexadecane) has acetane number (CN) of 100. See, e.g., ASTM International Standard TestMethod D-613 for determining cetane number.

“Pour point,” as defined herein, represents the lowest temperature atwhich a fluid will pour or flow. See, e.g., ASTM International StandardTest Methods D 5950-96, D 6892-03, and D 97.

“Cloud point,” as defined herein, represents the temperature at which afluid begins to phase separate due to crystal formation. See, e.g., ASTMStandard Test Methods D 5773-95, D 2500, D 5551, and D 5771.

As used herein, “carbon number” or “Cn,” where “n” is an integer,describes a hydrocarbon or hydrocarbon-containing molecule or fragment(e.g., an alkyl or alkenyl group) wherein “n” denotes the number ofcarbon atoms in the fragment or molecule—irrespective of linearity orbranching.

3. Fuel Compositions

As already mentioned, the novel biodiesel fuel compositions describedherein generally comprise an ester-based biodiesel (fuel) component anda functionalized ester component, wherein the functionalized estercomponent comprises a quantity of functionalized ester-based species.The functionalized ester species, in the biodiesel fuel compositions ofthe present invention, provide improved low-temperature properties tothe biodiesel fuels in which they reside, thereby rendering such fuels“enhanced.”

In some embodiments, the present invention is directed to one or moreenhanced biodiesel fuel compositions, said compositions comprising: (a)an ester-based biodiesel component; and (b) a functionalized estercomponent comprising functionalized ester species having the generalformula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; wherein R₂ and R₃ are independently selected from the groupconsisting of C1 to C10 alkyl moieties, C1 to C10 alkenyl moieties, andcombinations thereof; wherein R₄ is selected from the group consistingof C2 to C20 alkyl moieties and C2 to C20 alkenyl moieties; wherein R₅is selected from the group consisting of —H, hydroxyl (—OH), and C2 toC20 ester-forming carboxylate (RCOO—) functional species/moieties; andwherein the functionalized ester species amount to at least about 0.1weight percent of the enhanced biodiesel fuel.

In some such above-described embodiments, the functionalized esterspecies function as pour point depressants. Operating in this manner,such species impart low-temperature property improvement to the fuel bylowering the temperature at which the fuel composition will continue toflow (vide supra).

In some such above-described embodiments, the enhanced biodiesel fuelcomposition has a pour point of less than about −5° C., in otherembodiments it is less than −7° C., and in still other embodiments it isless than −9° C. Perhaps correspondingly, in some or other embodiments,the above-described enhanced biodiesel fuel composition has a cloudpoint of less than 7° C., in other embodiments it is less than 5° C.,and in still other embodiments it is less than 4° C. Those of skill inthe art will recognize that environmental, regional, and regulatoryfactors, as well as the fuel's intended use, may provide a need and/ordesire for specific pour point and cloud point thresholds/limits.

In some such above-described embodiments, the enhanced biodiesel fuelcomposition further comprises epoxy-ester species, wherein suchepoxy-ester species account for at least about 0.5 weight percent of theenhanced biodiesel fuel composition, and wherein such species functionas combustion improvers in said enhanced biodiesel fuel composition. Insome other embodiments, such epoxy-ester species account for at leastabout 2 weight percent of the enhanced biodiesel fuel composition. Instill other embodiments, such epoxy-ester species account for at leastabout 5 weight percent of the enhanced biodiesel fuel composition.

In some such above-described embodiments (whether comprising epoxy-esterspecies or not), the enhanced biodiesel fuel composition has a cetanerating of at least about 40 and at most about 55. In other embodiments,the enhanced biodiesel fuel composition has a cetane rating of at leastabout 45. In still other embodiments, the enhanced biodiesel fuelcomposition has a cetane rating of at least about 50. While regulatoryfactors may require cetane numbers over 50, it is worth noting thatcetane numbers greater than 55 often have little additional commercialvalue or benefit.

4. Methods of a First Type

As mentioned above, in some embodiments the present invention isdirected to one or more methods of a first type for making suchabove-described enhanced fuel compositions and, by extension, to methods(also of a first type) for improving the low-temperature properties of abiodiesel fuel composition.

Referring to FIG. 1, in some embodiments, such above-described methodsof a first type for improving low-temperature properties of biodieselfuels comprise the steps of: (Step 101) providing a biodiesel fuelcomprising unsaturated ester molecules; (Step 102) treating thebiodiesel fuel so as to react at least some of the unsaturated estermolecules contained therein with an oxidizing species to convert atleast some of the unsaturated ester molecules to epoxy-ester species andprovide for an epoxy-ester-containing biodiesel fuel; and (Step 103)reacting at least some of the epoxy-ester species in theepoxy-ester-containing biodiesel fuel with one or more reactants toproduce an enhanced biodiesel fuel composition comprising functionalizedester species, wherein such enhancement of the biodiesel fuel at leastpartially results from an improvement in the low-temperature propertiesof said enhanced biodiesel fuel relative to those of the biodiesel fuelfrom which it was derived.

Typically, the biodiesel fuel is at least partially-derived from atriglyceride-containing biomass from which an ester-based biodiesel fuelcan be produced (vide supra). As mentioned above, fatty acid methylesters (FAME) is a representative such biofuel. In some suchabove-described embodiments, the biodiesel fuel is B100. In some orother such embodiments, the biodiesel fuel is a mixture of biodiesel andconventional petroleum diesel. In still other such embodiments, thebiodiesel fuel is a mixture of any combination of the following:ester-based biodiesel, non-ester-based biodiesel, and conventionalpetroleum diesel.

In some such above-described embodiments, the unsaturated estermolecules are present in the form of monounsaturated ester species,polyunsaturated ester species, and combinations thereof. In some suchembodiments, the unsaturated ester molecules account for at least 1weight percent of the biodiesel fuel. In other such embodiments, theunsaturated ester molecules account for at least 5 weight percent of thebiodiesel fuel. In still other such embodiments, the unsaturated estermolecules account for at least 10 weight percent of the biodiesel fuel.

In some such above-described embodiments, the unsaturated estermolecules are selected from species having the general formula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; and wherein R₂ and R₃ are independently selected from thegroup consisting of C1 to C10 alkyl moieties, C1 to C10 alkenylmoieties, and combinations thereof.

In some such above-described embodiments, the oxidizing species isselected from the group consisting of hydrogen peroxide, organicperoxides, peroxy acids, and combinations thereof. An exemplary suchorganic peroxide is chloroperoxybenzoic acid, but those of skill in theart will recognize that the specific peroxide is not specifically solimited and that one or more of a variety of peroxide species could alsobe suitably so employed.

In some such above-described embodiments, the epoxy-ester-containingbiodiesel fuel comprises a heterogeneous mixture of epoxy-ester speciesformed by the oxidation of a heterogeneous mixture of unsaturated estermolecules. Those of skill in the art will appreciate that suchheterogeneity can result from heterogeneity in the biomass source(s)and/or a result of blending two or more different types ofester-containing biodiesel fuels.

In some such above-described embodiments, the step of reacting theepoxy-ester species comprises a reacting substep of epoxide ring openingto form a dihydroxy ester. In some such embodiments, the epoxide ringopening involves an acid-catalyzed hydrolysis. In some such embodiments,such methods further comprise a reacting substep of esterifying one orboth hydroxyl groups of the dihydroxy ester species with anesterification species selected from the group consisting of carboxylicacids, acyl halides, acyl anhydrides, and combinations thereof. Examplesof such ring opening and such subsequent esterification (if desired) isdescribed in commonly-assigned U.S. patent application Ser. No.11/696,564.

In some such above-described embodiments, the step of reacting theepoxy-ester species comprises a direct esterification of at least someof the epoxy-ester species. Examples of such direct esterification aregiven in commonly-assigned U.S. patent application Ser. No. 12/023,695.

In some such above-described embodiments, the functionalized esterspecies comprise the general formula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; wherein R₂ and R₃ are independently selected from the groupconsisting of C1 to C10 alkyl moieties, C1 to C10 alkenyl moieties, andcombinations thereof; wherein R₄ is selected from the group consistingof C2 to C20 alkyl moieties and C2 to C20 alkenyl moieties; and whereinR₅ is selected from the group consisting of —H, hydroxyl (—OH), and C2to C20 ester-forming carboxylate (RCOO—) functional species/moieties.

Per the enhanced biodiesel fuels described above, in some embodimentsthe functionalized ester species amount to at least about 0.1 weightpercent of the enhanced biodiesel fuel. Further, in some suchembodiments the functionalized ester species function as pour pointdepressants in the enhanced biodiesel fuel.

Per the enhanced biodiesel fuels described above, in some suchabove-described embodiments, the enhanced biodiesel fuel has a pourpoint of less than about −5° C. In some such embodiments, the enhancedbiodiesel fuel has a cloud point of less than about 7° C.

In some embodiments, the above-described enhanced biodiesel fuelcomprises epoxy-ester species, wherein such epoxy-ester species compriseat least about 0.1 weight percent of the enhanced biodiesel fuel, andwherein such species function as combustion improvers in said enhancedbiodiesel fuel. In some such embodiments, such epoxy-ester speciescomprise at most about 10 weight percent of the enhanced biodiesel fuel.

In some such aforementioned embodiments, the epoxy-ester species presentin the enhanced biodiesel fuel are residual constituents, i.e.,epoxy-ester species that were not reacted to yield functionalized esterspecies. In some or other such aforementioned embodiments, theepoxy-ester species present in the enhanced biodiesel fuel are suppliedas additives, i.e., via a step of adding such species. Such epoxy-esterspecies can improve the overall combustion efficiency of the enhancedbiodiesel fuel composition. See commonly-assigned U.S. patentapplication Ser. No. 12/241,411.

Regardless of whether of not epoxy-ester species are added to the fuelcomposition, in some such above-described embodiments, the enhancedbiodiesel fuel has a cetane rating of at least about 40 and at mostabout 55.

5. Methods of a Second Type

As mentioned above, the present invention is also directed to one ormore methods of a second type for making the enhanced biodiesel fuelcompositions described above and, by extension, for improving thelow-temperature properties of biodiesel fuel compositions.

Referring to FIG. 2, in some embodiments, the present invention isdirected to one or more methods of a second type for improvinglow-temperature properties of a biodiesel fuel, said method comprisingthe steps of: (Step 201) providing a first biodiesel fuel comprisingunsaturated ester molecules; (Step 202) extracting at least some of theunsaturated ester molecules from the first biodiesel fuel so as toprovide an extract; (Step 203) treating the extract with an oxidizingspecies so to convert at least some of the unsaturated ester moleculescontained therein into epoxy-ester species and provide for anepoxy-ester-containing intermediate; (Step 204) reacting at least someof the epoxy-ester species in the epoxy-ester-containing intermediatewith one or more reactants to produce a functionalized ester compositioncomprising functionalized ester species; and (Step 205) adding thefunctionalized ester composition to a second biodiesel fuel so as toprovide for an enhanced biodiesel fuel.

In some such above-described embodiments, the first and second biodieselfuels are at least substantially the same. In some or other suchembodiments, the first and second biodiesel fuels are independentlyselected from B100 and one or more mixtures of biodiesel andconventional petroleum diesel.

In some such above-described embodiments, the step of extracting makesuse of a technique selected from the group consisting of solventdewaxing, fractional crystallization, and combinations thereof. Those ofskill in the art will recognize that a number of other known separationtechniques may also be suitably applicable for such extracting.Accordingly, extracting by any of such techniques should be consideredto fall within the scope of the present invention.

In some such above-described embodiments, the unsaturated estermolecules are any combination of monounsaturated ester species andpolyunsaturated ester species. Those of skill in the art will recognizethat the characteristics and distribution of such species are highlydependent on the biodiesel fuel from which they are extracted.

In some such above-described embodiments, the unsaturated estermolecules are selected from species having the general formula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; and wherein R₂ and R₃ are independently selected from thegroup consisting of C1 to C10 alkyl moieties, C1 to C10 alkenylmoieties, and combinations thereof.

In some such above-described embodiments, the oxidizing species isselected from the group consisting of hydrogen peroxide, organicperoxides, peroxy acids, and combinations thereof. An exemplary suchoxidizing species is chloroperoxybenzoic acid (vide supra).

In some such above-described embodiments, the epoxy-ester-containingintermediate comprises a heterogeneous mixture of epoxy-ester speciesformed by the oxidation of a heterogeneous mixture of unsaturated estermolecules. Those of skill in the art will appreciate that suchheterogeneity can result from heterogeneity in the biomass source(s)and/or a result of blending two or more different types ofester-containing biodiesel fuels.

In some such above-described embodiments, the step of reacting theepoxy-ester species comprises a reacting substep of epoxide ring openingto form a dihydroxy ester. In some such embodiments, the epoxide ringopening involves an acid-catalyzed hydrolysis. In some or other suchembodiments, there further comprises a reacting substep of esterifyingthe dihydroxy ester species (one or both hydroxyl groups) with anesterification species selected from the group consisting of carboxylicacids, acyl halides, acyl anhydrides, and combinations thereof.

In some such above-described embodiments, the step of reacting theepoxy-ester species comprises a direct esterification of at least someof the epoxy-ester species. Such direct esterification of epoxy-esterspecies is described in commonly-assigned U.S. patent application Ser.No. 12/023,695

In some such above-described embodiments, the functionalized esterspecies comprise the general formula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; wherein R₂ and R₃ are independently selected from the groupconsisting of C1 to C10 alkyl moieties, C1 to C10 alkenyl moieties, andcombinations thereof; wherein R₄ is selected from the group consistingof C2 to C20 alkyl moieties and C2 to C20 alkenyl moieties; and whereinR₅ is selected from the group consisting of —H, hydroxyl (—OH), and C2to C20 ester-forming carboxylate (RCOO—) functional species/moieties. Insome such embodiments, the enhanced biodiesel fuel comprises at leastabout 0.1 weight percent functionalized ester species. In some or othersuch embodiments, the functionalized ester species function as pourpoint depressants in the enhanced biodiesel fuel.

Per the enhanced biodiesel fuels described above, in some suchabove-described embodiments, the enhanced biodiesel fuel has a pourpoint of less than about −5° C. In some such embodiments, the enhancedbiodiesel fuel has a cloud point of less than about 7° C.

In some embodiments, the above-described enhanced biodiesel fuelcomprises epoxy-ester species, wherein such epoxy-ester species compriseat least about 0.1 weight percent of the enhanced biodiesel fuel, andwherein such species function as combustion improvers in said enhancedbiodiesel fuel. In some such embodiments, such epoxy-ester speciescomprise at most about 10 weight percent of the enhanced biodiesel fuel.

In some such aforementioned embodiments, the epoxy-ester species presentin the enhanced biodiesel fuel are residual constituents, i.e.,epoxy-ester species that were not reacted to yield functionalized esterspecies. In some or other such aforementioned embodiments, theepoxy-ester species present in the enhanced biodiesel fuel are suppliedas additives, i.e., via a step of adding such species. Such epoxy-esterspecies can improve the overall combustion efficiency of the enhancedbiodiesel fuel composition. See commonly-assigned U.S. patentapplication Ser. No. 12/241,411.

Regardless of whether or not epoxy-ester species are added to the fuelcomposition, in some such above-described embodiments, the enhancedbiodiesel fuel has a cetane rating of at least about 40 and at mostabout 55.

6. Variations

While the above-described embodiments have been directed to enhancedbiodiesel fuel compositions and methods for improving the performance ofbiodiesel fuels, variations on such embodiments could extend to otherwholly or partially bio-derived transportation fuels and/or heatingfuels.

While the above-described embodiments have been largely directed tocompositions and methods comprising ester-functionalized ester species(di- and tri-ester species), other functionalization routes are possiblevia the epoxy-ester species and/or some other intermediate.Additionally, the dihydroxy ester species mentioned above could alsoserve as a pour point depressant without further functionalization.

In some various embodiments, some or all of the ester-based biofuels arederived from animal fats, in addition to, or in lieu of, crop-basedsources.

In some various embodiments, the present invention is directed to one ormore methods of improving the low-temperature properties of one or morebiofuels irrespective of the biofuel compositions that result from suchmethods.

7. EXAMPLES

The following examples are provided to demonstrate particularembodiments of the present invention. It should be appreciated by thoseof skill in the art that the methods disclosed in the examples whichfollow merely represent exemplary embodiments of the present invention.However, those of skill in the art should, in light of the presentdisclosure, appreciate that many changes can be made in the specificembodiments described and still obtain a like or similar result withoutdeparting from the spirit and scope of the present invention.

Example 1

This Example serves to illustrate a method of forming epoxy-esterspecies from biodiesel, in accordance with some embodiments of thepresent invention.

In this procedure, soy methyl ester (FAME derived from soybean oil) isused as the biodiesel/biofuel comprising unsaturated ester species to beepoxidized. The unsaturated ester species contained therein is oleicacid methyl ester (methyl oleate), CH₃(CH₂)₇CH═CH(CH₂)₇COOCH₃. Therelative amounts can be determined by gas-chromatography/massspectrometry (GC/MS) analysis.

With reference to FIG. 3, approx. 300 g of homogenized soy methyl ester(1) is weighed and transferred into a flask via a funnel. Whilestirring, 750 mL of methylene chloride (CH₂Cl₂) and 107 g ofmeta-chloroperoxybenzoic acid (2) (mCPBA, ˜70-75%) (ClC₆H₄COOOH) isadded to the flask (over a period of ˜20 min.) which is subsequentlystoppered. After suitable reaction time, the reaction mixture isfiltered and the filtrate collected. Any visible water in the filtrateis removed with anhydrous MgSO₄, after which the filtrate isre-filtered.

The above-mentioned filtrate is transferred to a 2000 mL round bottomflask from which the methylene chloride is removed via rotaryevaporation. Approx. 750 mL of hexanes are added to the residue withheating (˜60° C.) until the residue is re-dissolved. The resultingsolution is then transferred to a separatory funnel where it is washedtwice with 750 mL of deionized (DI) water, twice with 700 mL of 10%potassium bicarbonate solution (KHCO₃), once (again) with 500 mL of DIwater, and finally once with 700 mL of saturated sodium chloridesolution (brine) to yield a washed organic phase. The washed organicphase is filtered with a D-glass Büchner frit, and the resultingfiltrate is subjected to rotary evaporation to yield an oily productmixture comprising the epoxy-ester species (3) and palmitic methylester, wherein the epoxy-ester species has been determined to be presentin an amount equal to about 30% of the product mixture, as determined bysubsequent GC/MS analysis.

Example 2

This Example serves to illustrate conversion of epoxy-ester species tofunctionalized ester species, in accordance with some embodiments of thepresent invention.

Referring again to FIG. 3, the epoxy-ester species (3) generallyprovided for in EXAMPLE 1, is reacted with esterification agent (4) toyield functionalized ester species (5), wherein an exemplaryesterification agent (4) is acetic anhydride, and wherein thefunctionalized ester species (5) can be a triester, a diester hydroxide,or a combination of the two.

To 200 mL of xylenes was added 82.6 g of propionic acid (C₂H₅COOH) and100 g of soy-derived epoxy-ester species (3) with stirring and heated atreflux for 2 hours. Approx. 1.24 mL of phosphoric acid (85%) was thenadded. After 16 hours under reflux, the xylenes were removed via rotaryevaporation. The remaining solution was washed 3× with 100 mL of 10%NaHCO₃ solution. The top (organic) layer was washed 3× with 250 mL ofdeionized water and then dried with anhydrous MgSO₄. The organic layerwas then filtered and rotary-evaporated to yield a 67.2 g solutioncontaining functionalized ester species (5).

Example 3

This Example serves to illustrate how methods/compositions of thepresent invention can be used to improve the low-temperature propertiesof biodiesel fuels, in accordance with some embodiments of the presentinvention.

A B10 soy-based FAME biodiesel was prepared having a pour point of −15C.Adding 1 weight percent enhanced biodiesel soy-derived fuel composition(comprising ˜29 weight percent functionalized ester species) reduced thepour point to −19° C.

8. Conclusion

The foregoing describes enhanced biodiesel fuel compositions havingimproved low-temperature properties. The present invention isadditionally directed to methods for making such enhanced biodieselfuels by improving the low-temperature properties of ester-basedbiodiesel fuels via in situ enhancement/modification and/or additiveenhancement. Such compositions and methods extend the utility ofester-based biodiesel fuels to colder climates (geographically andseasonally).

All patents and publications referenced herein are hereby incorporatedby reference to an extent not inconsistent herewith. It will beunderstood that certain of the above-described structures, functions,and operations of the above-described embodiments are not necessary topractice the present invention and are included in the descriptionsimply for completeness of an exemplary embodiment or embodiments. Inaddition, it will be understood that specific structures, functions, andoperations set forth in the above-described referenced patents andpublications can be practiced in conjunction with the present invention,but they are not essential to its practice. It is therefore to beunderstood that the invention may be practiced otherwise than asspecifically described without actually departing from the spirit andscope of the present invention as defined by the appended claims.

1. A method for improving low-temperature properties of a biodieselfuel, said method comprising the steps of: a) providing a firstbiodiesel fuel comprising unsaturated ester molecules; b) extracting atleast some of the unsaturated ester molecules from the first biodieselfuel so as to provide an extract; c) treating the extract with anoxidizing species so to convert at least some of the unsaturated estermolecules contained therein into epoxy-ester species and provide for anepoxy-ester-containing intermediate; d) reacting at least some of theepoxy-ester species in the epoxy-ester-containing intermediate with oneor more reactants to produce a functionalized ester compositioncomprising functionalized ester species; and e) adding thefunctionalized ester composition to a second biodiesel fuel so as toprovide for an enhanced biodiesel fuel.
 2. The method of claim 1,wherein the first and second biodiesel fuels are at least substantiallythe same.
 3. The method of claim 1, wherein the first and secondbiodiesel fuels are independently selected from B100 and one or moremixtures of biodiesel and conventional petroleum diesel.
 4. The methodof claim 1, wherein the step of extracting makes use of a techniqueselected from the group consisting of solvent dewaxing, fractionalcrystallization, and combinations thereof.
 5. The method of claim 1,wherein the unsaturated ester molecules are selected from the groupconsisting of monounsaturated ester species, polyunsaturated esterspecies, and combinations thereof.
 6. The method of claim 1, wherein theunsaturated ester molecules are selected from species having the generalformula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; and wherein R₂ and R₃ are independently selected from thegroup consisting of C1 to C10 alkyl moieties, C1 to C10 alkenylmoieties, and combinations thereof.
 7. The method of claim 6, whereinthe oxidizing species is selected from the group consisting of hydrogenperoxide, organic peroxides, peroxy acids, and combinations thereof. 8.The method of claim 7, wherein the epoxy-ester-containing intermediatecomprises a heterogeneous mixture of epoxy-ester species formed by theoxidation of a heterogeneous mixture of unsaturated ester molecules. 9.The method of claim 6, wherein the step of reacting the epoxy-esterspecies comprises a reacting substep of epoxide ring opening to form adihydroxy ester.
 10. The method of claim 9, wherein the epoxide ringopening involves an acid-catalyzed hydrolysis.
 11. The method of claim9, further comprising a reacting substep of esterifying the dihydroxyester species with an esterification species selected from the groupconsisting of carboxylic acids, acyl halides, acyl anhydrides, andcombinations thereof.
 12. The method of claim 6, wherein the step ofreacting the epoxy-ester species comprises a direct esterification of atleast some of the epoxy-ester species.
 13. The method of claim 6,wherein the functionalized ester species comprise the general formula:

wherein R₁ is selected from the group consisting of C1 to C3 alkylmoieties; wherein R₂ and R₃ are independently selected from the groupconsisting of C1 to C10 alkyl moieties, C1 to C10 alkenyl moieties, andcombinations thereof; wherein R₄ is selected from the group consistingof C2 to C20 alkyl moieties and C2 to C20 alkenyl moieties; wherein R₅is selected from the group consisting of —H, hydroxyl, and C2 to C20ester-forming carboxylate functional moieties;
 14. The method of claim13, wherein the enhanced biodiesel fuel comprises at least about 0.1weight percent functionalized ester species.
 15. The method of claim 14,wherein the functionalized ester species function as pour pointdepressants in the enhanced biodiesel fuel.
 16. The method of claim 14,wherein the enhanced biodiesel fuel has a pour point of less than about−5° C.
 17. The method of claim 14, wherein the enhanced biodiesel fuelhas a cloud point of less than about 7° C.
 18. The method of claim 13,wherein the enhanced biodiesel fuel comprises epoxy-ester species,wherein such epoxy-ester species comprise at least about 0.1 weightpercent of the enhanced biodiesel fuel, and wherein such speciesfunction as combustion improvers in said enhanced biodiesel fuel. 19.The method of claim 18, wherein such epoxy-ester species comprise atmost about 10 weight percent of the enhanced biodiesel fuel.
 20. Themethod of claim 18, wherein the epoxy-ester species present in theenhanced biodiesel fuel are residual constituents in the functionalizedester composition.
 21. The method of claim 18, wherein the epoxy-esterspecies present in the enhanced biodiesel fuel are supplied asadditives.
 22. The method of claim 19, wherein the enhanced biodieselfuel has a cetane rating of at least about 40 and at most about 55.